Growth of biological matter can be a problem for shingled roofs. For example, moss, mold, bacteria, and fungus can cause unsightly discoloration of the shingles. This matter can also shorten the lives of the shingles, requiring costly replacement.
Skilled artisans often place a biocidal source on the roof to prevent the growth of biological matter. Such biocidal sources usually include an ionic metal such as zinc, copper, or lead. The biocidal source is typically placed near the top of the roof in strips. Rainwater dissolves some of the biocide as it runs over the strip. The rainwater then carries the biocide over the shingles below the strip as the rainwater continues down the roof. The scattered biocide thus prevents the growth of unwanted biological matter below the strips.
Biocidal strips can be unsightly themselves. The strips have a metallic look that does not blend in with the shingles. In addition, a strip of biocidal source about one inch wide is required to provide proper coverage for just ten feet of shingles. Therefore, either a wide strip must be installed to cover an entire side of a typical roof, or several strips must be installed on each side of the roof.
In the prior art, Nielson attempted to avoid the use of strips in U.S. Pat. No. 4,276,732 by using a trough containing a biocidal source. The '732 patent is not subtle in appearance, however, due to its large size and metallic outer surface. In addition, the trough contains a series of small holes for water to drain out. The distance between the holes creates gaps in the water coverage as the water flows down the roof. Gaps in the water coverage can cause unsightly streaks on the roof.
Wolfert attempted to combine a biocidal source with a ridge vent in U.S. Pat. No. 4,554,862. The '862 ridge vent is composed primarily of zinc. Therefore, the invention has the problem of being aesthetically unappealing, like the zinc strips, because it stands out from the shingles due to the zinc's metallic appearance. In addition, the '862 invention discloses large gaps between the drain holes in the ridge vent. The large gaps can cause streaking due to uneven water coverage on the roof.